Impact-sensing thermal insulation system and missile incorporating same

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of commonly-owned, co-pending U.S. patent application Ser. No. 11/169,607, entitled “Fiber Optic Impact Sensing System and Method of Using Same” by inventor David L. Hunn, filed on 29 Jun. 2005, which is incorporated herein by reference for all purposes.

BACKGROUND

1. Field of the Invention

The present invention relates to an impact-sensing thermal insulation system.

2. Description of Related Art

Missiles, rockets, and other such vehicles use propellants that are often stored in pressure vessels within the vehicles. It is often desirable to thermally insulate such pressure vessels to protect the pressure vessels from aerodynamic heating during flight, which can undermine the structural integrity of the pressure vessels.

Moreover, it is important to avoid mechanically damaging pressure vessels. It is, however, inevitable that some damage will occur to such members during use. Sometimes it is not known that damage has occurred to a pressure vessel. In such situations, the pressure vessel may fail upon use without warning. At other times, it may be known that damage has occurred but it is not known whether the damage is extensive enough to compromise the structural integrity of the pressure vessel. Often, sophisticated testing is required to determine whether the pressure vessel is structurally sound for its intended purpose. Accordingly, it is often desirable to monitor the structural “health” of such pressure vessels so that the likelihood of a catastrophic failure can be minimized.

The structural integrity of composite pressure vessels, such as those made from materials comprising strands or filaments of structural fibers disposed in a polymeric matrix, may be particularly compromised if such a pressure vessel is mechanically damaged. Optical sensor arrays have been developed that can be embedded at discrete locations within a composite member to measure the internal strain of the member during use. Such sensors, however, provide no information as to the structural health of the member prior to use, because an unacceptable strain level may only be encountered during use. Moreover, these sensors fail to provide any information concerning external, impact-induced damage because they are disposed within the member.

While there are many thermal insulation systems well known in the art, considerable room for improvement remains.

DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the invention are set forth in the appended claims. However, the invention itself, as well as, a preferred mode of use, and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, in which the leftmost significant digit(s) in the reference numerals denote(s) the first figure in which the respective reference numerals appear, wherein:

<figref idref="DRAWINGS">FIG. 1</figref> is a stylized, side, elevational view of a missile incorporating an impact-sensing, thermal insulation system;

<figref idref="DRAWINGS">FIG. 2</figref> is a stylized, schematic representation of a first illustrative embodiment of the impact-sensing, thermal insulation system, applied to a pressure vessel of the missile of <figref idref="DRAWINGS">FIG. 1</figref>;

<figref idref="DRAWINGS">FIG. 3</figref> is a cross-sectional view, taken along the line <b>3</b>-<b>3</b> of <figref idref="DRAWINGS">FIG. 2</figref>, of a portion of the pressure vessel and an illustrative configuration of a optically-transmissive insulation of the impact-sensing, thermal insulation system of <figref idref="DRAWINGS">FIG. 2</figref>, illustrating one particular placement configuration of an optical fiber of the optically-transmissive insulation;

<figref idref="DRAWINGS">FIGS. 4A-4C</figref> are graphical representations of the light amplitude detected by a detector of the impact-sensing, thermal insulation system over a period of time in which an impact occurs for various scenarios;

<figref idref="DRAWINGS">FIGS. 5-8</figref> are cross-sectional views, corresponding to the view of <figref idref="DRAWINGS">FIG. 3</figref>, illustrating alternative placement configurations of the optical fiber of the optically-transmissive insulation;

<figref idref="DRAWINGS">FIG. 9</figref> is a stylized, schematic representation of a second illustrative embodiment of an impact-sensing, thermal insulation system, applied to a pressure vessel of the missile of <figref idref="DRAWINGS">FIG. 1</figref>; and

<figref idref="DRAWINGS">FIG. 10</figref> is a stylized, schematic representation of a third illustrative embodiment of an impact-sensing, thermal insulation system, applied to a pressure vessel of the missile of <figref idref="DRAWINGS">FIG. 1</figref>.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

The present invention represents an impact-sensing, thermal insulation system for a pressure vessel used in the propulsion system of a missile or rocket. As used herein, the term “missile” means a missile, rocket, or other such vehicle. The system includes an optically-transmissive, thermal insulation, which comprises one or more optical fibers wound about the pressure vessel to form a plurality of adjacent layers. The one or more optical fibers may be disposed adjacent an outer surface of the pressure vessel or may be embedded in the outer surface of the pressure vessel. Light is propagated through the one or more optical fibers. If the member suffers an impact, one or more of the optical fibers are compromised to an extent corresponding to the intensity of the impact, resulting in a corresponding decrease in the amplitude of light propagated through the optical fibers. The level of propagated light is monitored to determine if an impact has occurred and the magnitude of the impact.

<figref idref="DRAWINGS">FIG. 1</figref> depicts a missile <b>101</b> comprising a pressure vessel <b>103</b> for containing propellant in fluid communication with a motor <b>105</b>. Pressure vessel <b>103</b> and motor <b>105</b> comprise a propulsion system <b>107</b> of missile <b>101</b>, which propels missile <b>101</b> during flight.

<figref idref="DRAWINGS">FIG. 2</figref> depicts a first illustrative embodiment of an impact-sensing, thermal insulation system <b>109</b> operably associated with pressure vessel <b>103</b>. In its most basic form, impact-sensing, thermal insulation system <b>109</b> includes an optically-transmissive insulation <b>203</b>, a light source <b>205</b>, a detector <b>207</b>, an optical fiber <b>209</b> extending between insulation <b>203</b> and light source <b>205</b>, and an optical fiber <b>211</b> extending between insulation <b>203</b> and detector <b>207</b>. Note that insulation <b>203</b> is represented as a hatched area in <figref idref="DRAWINGS">FIG. 2</figref>. Insulation <b>203</b> comprises a plurality of layers of one or more optical fibers disposed about pressure vessel <b>103</b>, as is discussed in greater detail herein. Insulation <b>203</b> is disposed adjacent an outer surface <b>213</b> of pressure vessel <b>103</b>. Light from light source <b>205</b> propagates through optical fiber <b>209</b>, insulation <b>203</b>, and optical fiber <b>211</b> to detector <b>207</b>, as indicated by arrows <b>215</b>, <b>217</b>. Note that light emitted from light source <b>205</b> may exhibit wavelengths within the human visual spectrum or may exhibit wavelengths outside the human visible spectrum.

<figref idref="DRAWINGS">FIG. 3</figref> depicts one particular exemplary configuration of optically-transmissive insulation <b>203</b>. In the illustrative configuration, an optical fiber <b>301</b> is wound about pressure vessel <b>103</b> to form a plurality of adjacent layers <b>303</b>, <b>305</b>, and <b>307</b>. It should be noted that optical fiber <b>301</b> may comprise a plurality of optical fibers connected in an end-to-end fashion. As the number of layers, such as layers <b>303</b>, <b>305</b>, and <b>307</b>, is implementation-specific, the present invention contemplates any suitable number of layers of optical fiber <b>301</b>. A first end of optical fiber <b>301</b> is in optical communication with optical fiber <b>209</b> (shown in <figref idref="DRAWINGS">FIG. 2</figref>) and a second end of optical fiber <b>301</b> is in optical communication with optical fiber <b>211</b> (shown in <figref idref="DRAWINGS">FIG. 2</figref>). In the illustrative configuration, a protective coating <b>309</b> is disposed over layer <b>307</b> to protect optical fiber <b>301</b> from inadvertent damage. Protective coating <b>309</b> may comprise, for example, a paint or a syntactic foam. Other configurations of optically-transmissive insulation <b>203</b> are contemplated by the present invention and examples of such configurations are discussed herein and shown in the drawings.

Generally, if pressure vessel <b>103</b> sustains an impact, optical fiber <b>301</b> of optically-transmissive insulation <b>203</b> will be damaged to some degree corresponding to the intensity of the impact. The amount of damage to optical fiber <b>301</b> is, in general, inversely proportional to the amplitude of light propagated through optical fiber <b>301</b>. <figref idref="DRAWINGS">FIGS. 4A-4C</figref> illustrate three particular exemplary scenarios that might be encountered during the operation of system <b>109</b> (shown in <figref idref="DRAWINGS">FIG. 2</figref>). Each of <figref idref="DRAWINGS">FIGS. 4A-4C</figref> provides a graphical representation of the light amplitude detected by detector <b>207</b> over a period of time in which an impact occurs. Also, shown in each of <figref idref="DRAWINGS">FIGS. 4A-4C</figref> is a graphical representation of a predetermined threshold value <b>401</b>. Light amplitudes detected by detector <b>207</b> that are greater than threshold value <b>401</b> are interpreted as resulting from impacts that will not structurally compromise pressure vessel <b>103</b> and are, thus, acceptable. It should be noted that light amplitudes detected by detector <b>207</b> may be considered acceptable if they are greater than the threshold <b>401</b> within a certain tolerance band, or, in other words, greater than about the threshold <b>401</b>. Light amplitudes detected by detector <b>207</b> that are less than threshold <b>401</b> are considered unacceptable, as the light amplitudes correspond to impacts that may structurally compromise pressure vessel <b>103</b>. Note that light amplitudes detected by detector <b>207</b> may be considered unacceptable if they are less than the threshold <b>401</b> within a certain tolerance band, or, in other words, less than about the threshold <b>401</b>.

<figref idref="DRAWINGS">FIG. 4A</figref> illustrates a scenario wherein pressure vessel <b>103</b> sustains an impact of sufficient magnitude to severely damage optical fiber <b>301</b> (shown in <figref idref="DRAWINGS">FIG. 3</figref>). In this example, optical fiber <b>301</b> is damaged at about time T₁to a degree that little light is propagated therethrough and detected by detector <b>207</b>. The light amplitude detected by detector <b>207</b> after time T₁falls well below threshold value <b>401</b>. Accordingly, the structural integrity of pressure vessel <b>103</b> has been sufficiently compromised, due to the impact, that pressure vessel <b>103</b> must be replaced or repaired. Detector <b>207</b> is operable to provide an indication that a significant impact has occurred.

<figref idref="DRAWINGS">FIG. 4B</figref> illustrates a situation wherein pressure vessel <b>103</b> sustains an impact of sufficient magnitude to damage optical fiber <b>301</b> to a lesser degree than shown in <figref idref="DRAWINGS">FIG. 4A</figref>. In this example, optical fiber <b>301</b> is damaged at about time T₂such that the light amplitude detected by detector <b>207</b> falls just below threshold value <b>401</b>. Even though optical fiber <b>301</b> is not as severely damaged as in the example of <figref idref="DRAWINGS">FIG. 4A</figref>, the light amplitude detected by detector <b>207</b> indicates that the structural integrity of pressure vessel <b>103</b> has been sufficiently compromised to warrant replacement or repair. Detector <b>207</b> is operable to provide an indication that a significant impact has occurred.

<figref idref="DRAWINGS">FIG. 4C</figref> illustrates a scenario wherein pressure vessel <b>103</b> sustains an impact of sufficient magnitude to damage optical fiber <b>301</b> but to a lesser degree than shown in <figref idref="DRAWINGS">FIG. 4B</figref>. In this example, optical fiber <b>301</b> is damaged at about time T₃such that the light amplitude detected by detector <b>207</b> falls above threshold value <b>401</b>. Even though optical fiber <b>301</b> is somewhat damaged, the light amplitude detected by detector <b>207</b> indicates that the structural integrity of pressure vessel <b>103</b> has not been sufficiently compromised to warrant replacement or repair. Detector <b>207</b> is operable to provide an indication that an insignificant impact has occurred.

<figref idref="DRAWINGS">FIGS. 5-8</figref> depict configurations of optically-transmissive insulation <b>203</b> alternative to the configuration shown in <figref idref="DRAWINGS">FIG. 3</figref>. In the configuration of <figref idref="DRAWINGS">FIG. 5</figref>, optical fiber <b>301</b> is bonded to outer surface <b>213</b> of pressure vessel <b>103</b> by a resin or adhesive <b>501</b>, which substantially completely envelopes optical fiber <b>301</b>. In the configuration of <figref idref="DRAWINGS">FIG. 6</figref>, optical fiber <b>301</b> is bonded to outer surface <b>213</b> of pressure vessel <b>103</b> by a resin or adhesive <b>601</b>. Many composite pressure vessels such as pressure vessel <b>103</b> are fabricated using a filament winding process. In one embodiment, optical fiber <b>301</b> is applied to outer surface <b>213</b> of pressure vessel <b>103</b> during the filament winding process, such that resin <b>601</b> is applied to optical fiber <b>301</b> prior to being applied to outer surface <b>213</b>. When assembled pressure vessel <b>103</b> is cured, optical fiber <b>301</b> is bonded to outer surface <b>213</b>. In the embodiment illustrated in <figref idref="DRAWINGS">FIG. 6</figref>, a thin, protective covering or layer <b>603</b> is disposed over layer <b>307</b> of optical fiber <b>301</b> to protect optical fiber <b>301</b> from incidental damage. Protective layer <b>603</b> may comprise, for example, a paint or a syntactic foam.

As shown in <figref idref="DRAWINGS">FIG. 7</figref>, one or more layers <b>303</b>, <b>303</b>, and <b>307</b> of optical fiber <b>301</b> may partially extend into pressure vessel <b>103</b>, especially if co-applied using a filament winding process. In such embodiments, a protective layer <b>701</b> may be disposed over optical fiber <b>301</b>, as discussed above. Alternatively, all layers <b>303</b>, <b>305</b>, and <b>307</b> of optical fiber <b>301</b> may be substantially fully embedded in pressure vessel <b>103</b>, as shown in <figref idref="DRAWINGS">FIG. 8</figref>. Other configurations are contemplated by the present invention.

<figref idref="DRAWINGS">FIG. 9</figref> depicts a second, illustrative embodiment of an impact-sensing, thermal insulation system <b>901</b>. In this embodiment, light source <b>205</b> is optically coupled by an optical fiber <b>903</b> to a fiber coupler <b>905</b>. Detector <b>207</b> is optically coupled by an optical fiber <b>907</b> to fiber coupler <b>905</b>. Fiber coupler <b>905</b> optically combines optical fibers <b>903</b>, <b>907</b> into a single optical fiber <b>909</b>. Optical fiber <b>909</b> operates in a “duplex” or “bidirectional” fashion, allowing light to independently propagate in two directions, as indicated by arrow <b>911</b>. Fiber coupler <b>905</b> is optically coupled with optically-transmissive insulation <b>203</b>, shown as hatched area in <figref idref="DRAWINGS">FIG. 9</figref>, via optical fiber <b>909</b>.

Light is emitted from light source <b>205</b> and propagates (as indicated by arrow <b>913</b>) through optical fiber <b>903</b> to fiber coupler <b>905</b>. The light is then propagated through optical fiber <b>909</b> to a distal end of optical fiber <b>301</b> (shown in FIGS. <b>3</b> and <b>5</b>-<b>8</b>) of optically-transmissive insulation <b>203</b>, where it is reflected. The reflected light then propagates through optical fiber <b>301</b> of insulation <b>203</b> and optical fiber <b>909</b> to fiber coupler <b>905</b>, where the reflected light is directed into optical fiber <b>907</b>. The reflected light propagates through optical fiber <b>907</b> (as indicated by arrow <b>917</b>) to detector <b>207</b>, where the amplitude of the reflected light is detected.

<figref idref="DRAWINGS">FIG. 10</figref> depicts a third illustrative embodiment of an impact-sensing, thermal insulation system <b>1001</b> according to the present invention. System <b>1001</b> is substantially identical to system <b>901</b> of <figref idref="DRAWINGS">FIG. 9</figref> except a second optical fiber <b>1003</b> (shown as a broken line in <figref idref="DRAWINGS">FIG. 10</figref>) is included to provide a redundant sensing capability. In this embodiment, optical fiber <b>301</b> of optically-transmissive insulation <b>203</b> is supplemented by a second optical fiber, such as optical fiber <b>311</b> of <figref idref="DRAWINGS">FIG. 3</figref>. Note that optical fiber <b>311</b> may be on the same layer, e.g., layer <b>303</b>, <b>305</b>, or <b>307</b> as optical fiber <b>301</b> or may be on a different layer and may be in any desired position on the layer. Light from light source <b>205</b> propagates bidirectionally through both optical fibers <b>909</b>, <b>1003</b>, as indicated by arrows <b>911</b> and <b>1005</b>, into optical fibers <b>301</b> and <b>311</b>, respectively of insulation <b>203</b>. The light is reflected from distal ends of optical fibers <b>301</b> and <b>311</b>, then propagates back through optical fibers <b>301</b> and <b>311</b> to optical fibers <b>909</b> and <b>1003</b>. Detector <b>207</b> detects the reflected light amplitude from both optical fibers <b>909</b> and <b>1003</b>.

The present invention provides significant advantages, including: (1) insulating a pressure vessel of a missile while providing the ability to assure the structural health of the pressure vessel prior to its use; and (2) insulating a pressure vessel of a missile while providing the ability to sense an external impact to the pressure vessel that may induce damage to the pressure vessel.

The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below. It is apparent that an invention with significant advantages has been described and illustrated. Although the present invention is shown in a limited number of forms, it is not limited to just these forms, but is amenable to various changes and modifications without departing from the spirit thereof.